Featured Invertebrate Data
Porpita porpita is considered to be uncommon in Okinawan waters, although it's commonly found at the *Wrack Line, washed up on numerous beaches during differing times of the year. I've seen numerous specimens on several Okinawan beaches and I've photographed and collected quite a few individuals over a period of many years of beach-crawling.
I've previously added several other surface-associated hydrozoans to the site:
The following description of Porpita porpita is taken from Wikipedia:
Porpita porpita, or blue button, is a marine organism consisting of a colony of hydroids found in tropical and sub-tropical waters of the Pacific, Atlantic, and Indian oceans. Although it is superficially similar to a jellyfish, each apparent individual is actually a colony of hydrozoan polyps. The blue button is a Chondrophore, which is a group of cnidarians that also includes Velella and Porpema. The chondrophores are similar to the better-known siphonophores, which includes the Portuguese man o' war, or Physalia physalis.
The blue button lives on the surface of the sea and consists of two main parts: the float and the hydroid colony. The hard golden brown float is round, almost flat, and about one inch wide. The hydroid colony, which can range from bright blue turquoise to yellow, resembles tentacles like those of the jellyfish. Each strand has numerous branchlets, each of which ends in knobs of stinging cells called nematocysts. The blue button sting is not powerful but may cause irritation to human skin.
The blue button itself is a passive drifter, and is part of the neustonic food web. It is preyed on by the sea slug Glaucus atlanticus (sea swallow or blue glaucus) and violet sea-snails of the genus Janthina. It competes with other drifters for food and mainly feeds on copepods and crustacean larvae. The blue button has a single mouth located beneath the float, which is used for both the intake of prey and the expulsion of wastes.
There are numerous on-line sites with photographs and videos of Porpita porpita. Several of these sites are:
Photos via Google
Videos via YouTube:
Blue Button Jellyfish Porpita Porpita [sic] At South Padre Island Texas
Porpita Porpita [sic]
porpita porpita [sic]
I've added a second page w/ a series of images of the species.
In addition, I've added a link to the current and past featured invertebrates via a list and thumbnails.
I've also upgraded the Okinawan Tidal Information sheet for 2019.
*Wrack Line: The wrack zone or "wrack line" is a coastal feature where organic material (e.g kelp, seagrass, shells) and other debris is deposited at high tide. This zone acts as a natural input of marine resources into a terrestrial system, providing food and habitat for a variety of coastal organisms.